This invention pertains to the field of control of hydrofoils on boats equipped with power or wind propulsion.
Automatic mechanical control of operational height above the water surface is a definite requirement for sailing hydrofoils where electronic or power equipment devices are either impractical, too complex, or not allowed. Attempts to satisfy this requirement have been directed toward sensing the water surface by floats, planing devices, drag surfaces, and V type control foils. All of these devices penetrate the water surface and depend on the load variations caused by changes in flotation volume or changes in wetted impact area of the device. All are prone to throwing spray which causes additional drag and discomfort to the crew. The floats, planers and drag devices are inherently inefficient and experience difficulties when the water surface is choppy. The V type foils are efficient in calm water but when it is choppy they are subject to intrusion of air into the low pressure area of the hydrofoil causing loss of lift, erratic control and low efficiency--this phenomena is called ventilation. The lack of an efficient height control system, free of ventilation problems may be the reason why sailing hydrofoils have not realized their full performance or commercial potential.